1. Field of the Invention
The present invention relates to a composite wood and a manufacturing method thereof. In particular, the present invention relates to a composite wood which has excellent characteristics similar to wood such as workability, excellent characteristics similar to synthetic resin such as water resistance and predetermined mechanical strength, and a manufacturing method thereof.
2. Discussion of the Related Art
Recently, environmental issues have been attracting attention. Especially, global warming due to carbon dioxide has being realized. Forest destruction caused by cutting trees has become a serious problem. In general, a cut tree is dried and lumbered. Then, the lumbered tree is worked in a shape or a configuration depending on various applications. In this way, lumber is obtained. Nevertheless, in most cases, the lumber is finally incinerated and is not effectively utilized.
On the other hand, generally available polyolefin-based thermoplastic resins such as polyethylene or polypropylene exhibit lipophilic properties and inferior wettability with respect to hydrophilic wood, pulp, paper, sawdust or the like. For this reason, these materials cannot be successfully mixed together. Even if these materials are forcibly mixed, the binding force between them is weak. Thus, it is difficult to manufacture a composite wood.
Various methods of manufacturing composite material such as fiber board, particle board, wood block or the like by using wood material and a thermoplastic resin such as a phenol resin or an epoxy resin have been proposed. Nevertheless, as these methods use the thermoplastic resin, costs are increased.
There has been proposed a method of crushing discarded wood, thinned wood or wood waste into wood powder, kneading the wood powder and melted polyolefin-based discarded plastic, extruding the kneaded material and forming the same. In this way, a product is manufactured and resources can be effectively utilized.                Japanese Examined Patent Publication No. S59(1984)-1304        Japanese Unexamined Patent Publication No. S58(1983)-217552        Japanese Examined Patent Publication No. S59(1984)-2455        Japanese Unexamined Patent Publication No. S59(1984)-217744        Japanese Examined Patent Publication No. H3(1991)-64553        Japanese Unexamined Patent Publication No. S61(1986)-155436        Japanese Unexamined Patent Publication No. H10(1998)-71636        
In accordance with the above-described method using the wood powder, the wood powder must be dried so as to have a predetermined amount of water content, e.g., 10% or less of the water content in order to ensure mechanical characteristics of composite wood. Thus, the manufacturing process is complicated.
If an amount of the wood powder is increased, the wood powder cannot be successfully kneaded with a melted resin. Actually, the amount of the wood powder is about the same as an amount of synthetic resin in volume ratio.
Although the wood powder is used for composite material, the composite material actually exhibits characteristics similar to a synthetic resin. Nailing, cutting by a saw, and adhesion using a water soluble adhesive are difficult. Further, applications for products which can be applied to the composite material are restricted.